U.S. Pat. No. 3,915,237 issued to E. J. Rozniecki on 28 October 1975 discloses a fire-suppressant system for a military vehicle that includes one or more thickwalled bottles containing fire-suppressant liquid, such as Halon 1301 (bromotrifluoromethane) pressurized to about 750 p.s.i. The system includes one or more optical fire detectors or sensors arranged within the vehicle to respond to emergent fireballs generated by passage of enemy projectiles through the vehicle fuel tank. The optical detector electrically triggers an explosive squib actuator for a fast-acting valve mounted on the fire-suppressant bottle.
One aim of the system disclosed in the patent is to suppress near-explosive fires within a very short period of time, e.g. one tenth of a second (100 milliseconds). To accomplish this aim it is necessary that the liquid fire-suppressant pressure be relatively high, on the order of 700-800 p.s.i. It is also necessary that the bottle discharge nozzle have a relatively large passage diameter, at least about 11/4 inch. With high liquid pressures and relatively large nozzle passage diameters it is possible to deliver relatively large quantities of fire-suppressant into the emergent fireball before the fireball propogates into unmanageable proportions.
The large mass flow rate of liquid fire-suppressant presents a problem in regard to personnel safety. Measurements taken with a load cell and impactor plate aligned on the nozzle axis show a liquid impact force of about 600 pounds at 1 inch from the nozzle exit opening. This force corresponds roughly to the force of a 16 pound bowling ball traveling at a speed of 40 miles per hour. Such a high impact force is sufficient to injure or knock down a soldier standing or crouching within the vehicle. The present invention seeks to minimize or reduce this impact force without seriously degrading the fire-suppression performance of the system.